7 Surprising Reasons People Pack on the Pounds

From the obvious to the unexpected. Do any sound familiar?

1. Poor planning at the buffet

Researchers at Cornell University observed patrons at all-you-can-eat buffets. They found that only 33 percent of obese customers checked out the full buffet before serving themselves, while 71 percent of normal-weight diners did so. So look before you leap: You'll be less likely to overfill your plate.

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2. A lack of sleep

A University of Colorado study found that although insufficient sleep can actually increase your body's metabolism, people who spent a week sleeping only five hours a night ate far more than those who slept nine hours. The short-sleepers gained an average of two pounds.

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3. Not relaxing enough

Stress causes many of us to eat more. A 2011 American Psychological Association survey found that about 40 percent of adults reported that when stressed they overeat or eat unhealthy foods.

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4. The excess of excess

Bacon cheeseburgers on a buttered glazed-doughnut bun? Peanut butter-and-bacon ice cream shakes? There have never been more opportunities to consume almost comically fattening products. Just say "no way"!

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5. Addictive foods

Frito-Lay's slogan for its potato chips was "Betcha can't eat just one!" That was a good bet: It's hard to stop once you get that taste of salt and carbs. In Salt Sugar Fat, Pulitzer-winning reporter Michael Moss describes how these addictive ingredients hook us on high-calorie, low-nutrient products.

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6. Drinking soda through a straw

As the Washington Postrecently noted, drinking straws have grown in diameter since the 1980s, from an estimated .21 inches to .28 inches. Bigger straws make it easier to suck up more sweet stuff. A mere 12 ounces of soda (a small serving these days) equals 8 to 13 teaspoons of sugar.

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7. A tiny breakfast and big dinner

A 2013 Israeli study found that overweight women who ate a big breakfast, moderate lunch and small dinner lost more than twice the weight as women who took in the same calories, but mostly at dinner. The maxim is true: Eat breakfast like a king, lunch like a prince and dinner like a pauper.